As the amount of information on the World Wide Web grows, the use of search engines to find relevant information becomes ever more critical. A search engine retrieves pages relevant to a user's query by comparing the attributes of pages, together with other features such as anchor text, and returns those that best match the query. The user is then typically shown a ranked list of Universal Resource Locators (URLs) of between 10 and 20 per page. The ranking of pages by search engines has proved to be a crucial component of how users browse the web. This situation arises not only from the simple gathering of information for users, but also from commercial transactions that result from the search activity.
Some commercial companies, to increase their website traffic, hire search engine optimization (SEO) companies to improve their site's ranking. There are numerous ways to improve a site's ranking, which may be broadly categorized as white-hat and gray-hat (or black-hat) SEO techniques. White-hat SEO methods focus on improving the quality and content of a page so that the information on the page is useful for many users. Such a method for improving a site's rank may be to improve the content of the site, such that it appears most relevant for those queries one would like to target.
However, there are many methods of improving ranking. Gray-hat and black-hat SEO techniques include methods such as link stuffing, keyword stuffing, cloaking, web farming, and so on. Link stuffing is the practice of creating many pages that have little content or duplicated content, all which link to a single optimized target page. Ranking based on link structure can be fooled by link-stuffed pages by thinking that the target page is a better page since so many pages link to it. Keyword stuffing is when a page is filled with query terms, making it appear very relevant to a search whose query contains one or more of those terms, even though the actual relevance of the page may be low. A keyword-stuffed page will rank higher since it appears to have content relevant to the query. For over-loaded terms on the page, the page will appear higher in the search results and will ultimately draw users to click on the site.
White-hat techniques can result in a better web search experience for a user. In particular, the user is provided with satisfactory results based on the original intent of the search query. In contrast, gray-hat or black-hat techniques can derail the user's search process in the hope of persuading the user to buy something they were not originally looking for.